Electric incandescent lamp filament support



Nov. 15, 1966 R. N. MALM ELECTRIC INCANDESCENT LAMP FILAMENT SUPPORT Filed July 1, 1964 w ITWVEETWLOTZ Roberfi: N. Malmn b H is A tovneg United States Patent Ofilice 3,286,116 Patented Nov. 15, 1966 3,286,116 ELECTRIC INCANDESCENT LAMP FILAMENT SUPPORT Robert N. Malm, Willoughby, Ohio, assignor to General Electric Company, a corporation of New York Filed July 1, 1964, Ser. No. 379,651 4 Claims. (Cl. 313-274) This invention relates in general to electric incandescent lamps and similar devices, and more particularly to means for supporting the lamp filament within the lamp envelope.

Certain types of electric incandescent lamps in general use at present comprise a tubular glass envelope or bulb containing a coiled tungsten filament extending longitudinally of the tubular envelope and electrically connected at its opposite ends to respective lead-in conductors which are sealed through the opposite ends of the tubular glass envelope. For certain applications where the lamp is ordinarily subjected to severe vibration such as is encountered, for example, in modern high speed aircraft service, it has been the customary practice to additionally support the filament of such lamps in place within the lamp envelope by means of one or more supplementary filament support means.

The most commonly used type of support heretofore employed for such purpose has comprised a threelegged wire support member consisting of three legs of twisted wire which are twisted tightly together upon the filament to extend radially outward thereof in a common transverse plane and which are anchored at their outer ends to the wall of the lamp envelope to support the filament in place therefrom. Such type filament supports may be formed in the manner and by the mechanism described and claimed in copending application Serial No. 109,322, now Patent No. 3,179,874, F. A. Mosby, filed May 11, 1961, and assigned to the assignee of the present invention. These twisted wire supports are preferably formed of tungsten wire and are assembled in place on the filament priort to the insertion of the latter into the tubular lamp envelope. To assure the effective supporting of the filament in place in the envelope, the filament with the three-legged twisted wire support fastened in place thereon is threaded or introduced endwise into the tubular lamp envelope and then adjusted in position therein to work or locate the free outer ends of the three twisted wire legs in respective outward locating dimples formed in the inside wall of the lamp envelope. However, because of the relatively brittle character of the twisted tungsten wire supported legs and their corresponding susceptibility to breakage, the use of such twisted tungsten Wire filament supports is not feasible in lamps employing relatively small diameter tubular envelopes having diameters less than /8 inch or so, the brittle tungsten wire support legs in such case frequently breaking off during the insertion and positioning of the filament in place within the tubular envelope.

It is an object of the invention therefore to provide an improved filament support for an electric incandescent lamp or similar device that will obviate the above-mentioned disadvantages of the prior support constructions.

Another object of the invention is to provide a'filament support for an electric incandescent lamp or similar device that will enable easy loading of the filament and its atrelease iodine for continuation of the cycle.

tached support into a tubular lamp envelope of considerably smaller inside diameter than possible heretofore without likelihood of breakage of the support.

Briefly stated, in accordance with one aspect of the invention, the filament support is comprised of a pair of refractory metal rods between which the filament is tightly clamped by refractory metal wire coil means or overwinds tightly wound around and binding the two support rods together in side-by-side relation extending crosswise of the filament.

In accordance with a further aspect of the invention, the wire coil overwinds on the two support rods are formed of a single length of wire, and the free ends of the support rods and wire coil overwinds are embedded in the wall of the lamp envelope to anchor the support thereto.

Further objects and advantages of the invention will appear from the following detailed description of a species thereof and from the accompanying drawing.

In the drawing, FIG. 1 is an elevation, partly in section, of an electric incandescent lamp provided with a filament support according to the invention, and

FIG. 2 is a transverse section on the line 2-2 of FIG. 1.

Referring to the drawing, the invention is there illustrated as applied to an electric incandescent lamp comprising an elongated tubular envelope 1, preferably of quartz tubing of small diameter, for example inch or less, and containing a helically coiled or coiled-coil tungsten wire filament 2 extending approximately axially of'the envelope 1. The filament is electrically connected and secured at its opposite ends to lead-in conductors 3 having extremely thin foliated portions (not shown) sealed in compressed pinch seal end portions of the envelope. The conductors 3 are suitably connected at their outer ends as by welding, for example, to metal contact terminals or base members 4 which are suitably secured to the pinch seal end portions of the envelope 1 as by means of a high temperature resistant basing cement such as, for example, that described and claimed in US. Patent 3,080,- 243, V. Vodicka, dated March 5, 1963.

The particular electric incandescent lamp illustrated is of the well-known iodine-cycle type as described and claimed in US. Patent 2,883,571, Fridrich and Wiley, the envelope 1 for such purpose containing, in addition to a suitable gas filling such as argon, krypton or xenon at a substantial pressure of, for example, 600 mm. Hg or above, a small amount of iodine vapor which functions as a regenerative getter during lamp operation to combine with tungsten vaporized from the filament 2 onto the envelope wall to thereby form a tungsten iodide which migrate back to the vicinity of the filament where it then dissociates to redeposit tungsten onto the filament and It should be understood, however, that the invention may be utilized as well in other types of electric incandescent lamps. Since such iodine-cycle lamps ordinarily operate at relatively high envelope or bulb wall temperatures, the envelope 1 of the lamp is preferably made of a high melting side of the envelope which tubulation is then tipped oif as indicated at 5 to hermetically seal the envelope.

The linear coiled or coiled-coil filament 2 is additionally supported at its mid-region by a supplamentary support means 6 which is securely fastened in place to the filament and is anchored to the wall of the lamp envelope 1. In accordance with the invention, the filament support means 6 is in the general form of a bridge member extending diametrically across the interior of the envelope 1 and comprises a pair of straight support rods 7 which extend in side-by-side relation across the filament 2 on opposite sides thereof and between which the filament is held or clamped tightly to thereby support it in place within the envelope 1.. The two support rods 7 are made of a suitable refractory metal, preferably tungsten wire of the diameter around 10 mils, and they are bound tightly together in side-by-side relation, to thereby clamp the filament 2 tightly therebetween, by wire coil means or overwinds 8 which are tightly wound around the respective end portions of the two side-by-side rods 6 at each side of the filament. The wire coil bindings or overwinds 8 are formed of a suitable refractory metal wire, for example, tungsten wire of a diameter around mils and, as shown, they are preferably constituted by a single continuous length of wire which is wound around the two side-by-side support rods 7 to form the substantially closed pitch end coil sections 8 joined together by a widely open pitch intermediate or central coil section 9 which extends over the mid-regions of the two support rods 7 where they cross the filament 2. Since the wire coil overwinds 8 are wound on the two side-by-side support rods 7, the resulting coil shape of the overwinds 8 is oval in cross section. As a result, the turns of the wire coil overwinds 8 cannot relax on the support rods 7 such as would permit these rods to become loose on the filament 2.

The filament support or bridge member 6 is anchored to the wall of the lamp envelope 1 to fixedly support it in place therein. For such purpose, the envelope 1 is formed with diametrically opposite locating dimples 10 in its inner Wall within which the opposite ends of the support member 6 are located or seated to thereby anchor them to the envelope wall. The support member 6 is made of a length slightly greater than the inside diameter of the envelope 1 in order to assure the extending thereof into the outward locating dimples 10 in the envelope wall. The ends of the filament support 6 are inserted and positioned within the locating dimples 10 during the loading of the filament 2 into the envelope 1, the filament with its previously attached support 6 being inserted endwise into one of the open ends of the tubular envelope 1 and then adjusted in position therein to work the opposite ends of the support 6 successively into the respective locating dimples 10 in the envelope wall. Preferably, the ends of the filament support 6 are embedded in the wall of the envelope 1 in order to positively anchor the support to the envelope and hold it in place therein. To accomplish this, the dimpled portions 10 of the envelope 1 are simply heated by gas fires directed thereagainst to soften and fuse them around the ends of the filament support 6. This embedding of the ends of the filament support 6 in the wall of the envelope 1 is preferably carried out right after the loading of the filament mount, comprised of the filament 2 with its attached lead-in conductors 3 and filament support 6, into the tubular envelope 1 and before the sealing of the lead-in conductors 3 into the opposite ends of the envelope.

The two-legged filament support 6 comprising my invention is of particular advantage over the three-legged twisted wire supports previously employed in that it permits loading of the filament mount into tubular envelopes 1 of considerably smaller diameter than possible heretofore without breakage of the legs of the filament support. Thus, whereas filament mounts provided with the prior three-legged filament support could not be loaded into tubular envelopes 1 much less than inch in diameter. without encountering an excessive amount of breakage of the legs of the filament support, filament mounts provided with supports 6 constructed according to the present invention can be loaded with ease into tubular envelopes of a diameter as little as inch with comparative freedom from breakage of the legs of the filament support. Presumably this is so because of the fact that the brittle tungsten wire of which these filament supports are customarily made is stressed to a much lower degree in the case of the two-legged support 6 of the present invention. Also, because the filament support 6 comprises the invention consists of only two supporting legs, instead of three legs as in the case of the prior filament support constructions, filament mounts provided with supports 6 according to the invention are much easier and less time-consuming and expensive to load into and position in place within the tubular envelope 1, the support 6 attached onto the filament 2 needing only to be temporarily skewed to a slightly angular position relative to the filament in order to permit the free and easy insertion of the filament mount endwise into the tubular envelope. Also, only two legs of the support 6 need be worked into position in the locating dimples 10 in the envelope wall as compared to three legs in the case of the prior three-legged filament supports.

Although a preferred embodiment of my invention has been disclosed, it will be understood that the invention is not to be limited to the specific construction and arrangement of parts shown, but that they may be widely modified within the spirit and scope of my invention as defined by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric incandescent lamp comprising a vitreous envelope, a pair of lead-in conductors extending into and hermetically sealed within said envelope, a coil refractory metal wire filament disposed in said envelope and electrically connected at its ends to said conductors, and a supplementary support for said filament comprising a pair of refractory meal support rods extending in side-by-side relation across and positioned on opposite sides of said filament and anchored at their opposite ends to the wall of said envelope, and wire coil means tightly wound around and binding together the respective end portions of the said side-by-side support rods at each side of said filament to thereby tightly clamp the filament therebetween.

2. An electric incandescent lamp comprising a vitreous envelope, a pair of lead-in conductors extending into and hermetically sealed within said envelope, a coiled refractory metal wire filament disposed in said envelope and electrically connected at its ends to said conductors, and a supplementary support for said filament comprising a pair of refractory metal support rods extending in side-by-sid-e relation across and positioned on opposite sides of said filament and anchored at their opposite ends to the wall of said envelope, and a length of wire tightly wound around and binding together the respective end portions of said side-by-side metal rods at each side of said filament to thereby tightly clamp the filament therebetween.

3. An electric incandescent lamp comprising a vitreous envelope, 2. pair of lead-in conductors extending into and hermetically sealed within said envelope, a coiled refractory metal wire filament disposed in said envelope and electrically connected at its ends to said conductors, and a supplementary support for said filament comprising a pair of refractory metal support rods extending in sideby-side relation across and positioned on opposite sides of said filament, a length of wire tightly wound around and binding together the respective end portions of said side-by-side metal rods at each side of said filament to thereby tightly clamp the filament therebetween, the opposite ends of said support rods and said wire length being embedded in the wall of said envelope.

4. An electric incandescent lamp comprising a tubular glass envelope, a pair of lead-in conductors extending into and sealed within opposite ends of said envelope, a linear coiled tungsten wire filament disposed within said envelope substantially coaxially thereof and connected at its opposite ends to said conductors, and a supplementary support for said filament comprising a pair of refactory metal support rods extending in side-by-side relation across and on opposite sides of said filament, and a length of wire tightly wound around and binding together the respective end portions of said side-by-side clamp the filament therebetween, the opposite ends of said support rods and said wire length being embedded in the Wall of said tubular envelope at approximately diametrically opposite points thereof.

No references cited.

JOHN W. HUCKERT, Primary Examiner.

metal rods at each side of said filament to thereby tightly 10 A. I. JAMES, Assistant Examiner. 

1. AN ELECTRIC INCANDESCENT LAMP COMPRISING A VITREOUS ENVELOPE, A PAIR OF LEAD-IN CONDUCTORS EXTENDING INTO AND HERMETICALLY SEALED WITHIN SAID ENEVELOPE, A COIL REFRACTORY METAL WIRE FILAMENT DISPOSED IN SAID CONDUSTORS, AND ELECTRICALLY CONNECTED AT ITS ENDS TO SAID CONDUCTORS, AND A SUPPLEMENTARY SUPPORT FOR SAID FILAMENT COMPRISING A PAIR OF REFRACTORY MEAL SUPPORT RODS EXTENDING IN SIDE-BY-SIDE RELATION ACROSS AND POSITIONED ON OPPOSITE SIDES OF SAID FILAMENT AND ANCHORED AT THEIR OPPOSITE ENDS TO THE WALL OF SAID ENVELOPE, AND WIRE COIL MEANS TIGHTLY WOUND AROUND AND BINDING TOGETHER THE RESPCTIVE END PORTIONS OF THE SIDE-BY-SIDE SUPPORT RODS AT EACH SIDE OF SAID FILAMENT TO THEREBY TIGHTLY CLAMP THE FILAMENT THEREBETWEEN. 